1. Field of the Invention
The present invention relates to a ratchet-action open-end wrench.
2. Description of the Prior Art
Conventional ratchet-action open-end wrench, as shown in U.S. Pat. No. 4,637,284, has a fixed jaw, a movable jaw which is able to slide linearly, and an elastic member. In an operation condition, user can pull the wrench back and forth. The movable jaw is able to reciprocate with respect to the fixed jaw. Thus, the movable jaw can clutch threaded member along only a predetermined direction, so that the threaded member is rotated along the predetermined direction. The threaded member would be released and would rotate with respect to the wrench when the wrench is pulled along the opposite direction. Threaded member can be detached or fastened easily.
However, the wrench mentioned above is not suitable for being used in a narrowed environment. Moving direction of the movable jaw is simply aimed away from the fixed jaw, even away from handle of the wrench. Considerable movement of the movable jaw is necessary for releasing the threaded member. Thus, the movable jaw would probably blocked by other objects, especially in narrowed environment, failing to move and to release the threaded member.
For the requirement of operation in narrowed space, wrenches are provided in several patents, such as U.S. Pat. Nos. 5,287,777, 5,582,082, and 7,827,887. These wrenches are suitable to be used in narrowed space, providing ratchet-action function. The wrench revealed in U.S. Pat. No. 5,287,777 is similar to the wrench revealed in U.S. Pat. No. 7,827,887. The movable jaws of the wrenches are slidable along a segmental pathway which is defined and limited by a pin, an arc-shaped hole, and several arc-shaped surfaces. Thus, the movable jaw is unable to rotate arbitrarily. The other wrench shown in U.S. Pat. No. 5,582,082 is provided with a pin and a linear extended hole, so that movable jaw of the wrench is able to slide. Further, both of movable jaw and fixed jaw of the wrench is formed with an arc-shaped surface. The arc-shaped surfaces are used for limiting sliding pathway of the movable jaw, so that the movable jaw can only slide with respect to the fixed jaw. The wrenches mentioned above are suitable for narrowed space, being welcomed in the market.
However, the wrenches are difficult to be produced. The components of the wrenches should be formed with several specific contours, especially arc-shaped surfaces, some of which are located in grooves. The arc-shaped surfaces are necessary for keeping the movable jaw in the predetermined pathway. The arc-shaped surfaces are very difficult to be machined or processed. For instance, the arc-shaped surface of the wrench described in U.S. Pat. No. 7,827,887 is located at an interior side of opening of the wrench. Machining tool, such as milling cutter, can hardly move into the opening. Thus, machining is obstructed.
For producing the wrenches, precision casting may be chosen as a main process. However, this would lead to a deterioration of quality of the wrench since precision casting is always accompanied with deficiencies about structure strength and surface precision. With lowered structure strength, the wrench would be unwelcomed in strict operation condition. With lowered surface precision, movement of movable jaw of the wrench would be obstructed by dust. On the other hand, precision casting would bring the manufacturing cost high. Market competitiveness of the wrenches would be probably destroyed by the disadvantages mentioned above.
The present invention is, therefore, arisen to obviate or at least mitigate the above mentioned disadvantages.